Balloon angioplasty is a medical procedure to widen obstructed blood vessels narrowed by plaque deposits. The procedure may be used in coronary or peripheral arteries. In an angioplasty procedure, a catheter having a special inflatable balloon on its distal end is navigated through the patient's arteries and is advanced through the artery to be treated to position the balloon within the narrowed region (stenosis). The region of the stenosis is expanded by inflating the balloon under pressure to forcibly widen the artery. After the artery has been widened, the balloon is deflated and the catheter is removed from the patient.
A significant difficulty associated with balloon angioplasty is that in a considerable number of cases the artery may again become obstructed in the same region where the balloon angioplasty had been performed. The repeat obstruction may be immediate (abrupt reclosure), which is usually caused by an intimal flap or a segment of plaque or plaque-laden tissue that loosens or breaks free as a result of the damage done to the arterial wall during the balloon angioplasty. Such abrupt reclosure may block the artery requiring emergency surgery which, if not performed immediately, may result in a myocardial infarction and, possibly, death. This risk also necessitates the presence of a surgical team ready to perform such emergency surgery when performing balloon angioplasty procedures. More commonly, a restenosis may occur at a later time, for example, two or more months after the angioplasty, for reasons not fully understood. This reclosure may require repeat balloon angioplasty or bypass surgery. When such longer term restenosis occurs, it usually is more similar to the original stenosis, that is, it is in the form of cell proliferation and renewed plaque deposition in and on the arterial wall.
To reduce the incidence of re-obstruction and restenosis, several strategies have been developed. Implantable devices, such as stents, have been used to reduce the rate of angioplasty related re-obstruction and restenosis by about half. The use of such intraluminal devices has greatly improved the prognosis of these patients. The stent is placed inside the blood vessel after the angioplasty has been performed. A catheter typically is used to deliver the stent to the arterial site to be treated. The stent may further include one or more therapeutic substance(s) impregnated or coated thereon to limit re-obstruction and/or restenosis.
Numerous stent designs are known in the art. A prior art ratchet-locking stent 100 design includes one or more, in this case one, interlocking part joined at a seam 102, as shown in FIGS. 1A and 1B, by one or more locking mechanisms 104 (e.g., locking tabs, ratcheting mechanisms, etc.). The part is formed as a flat sheet and folded upon itself to make up a tubular stent. One consideration in the design of the stent 100 relates to damage to the locking mechanisms 104. In some cases, during assembly, the exposed locking mechanisms may be susceptible to damage during the assembly and crimping (compressing) processes. As such, it would be desirable to provide a ratchet-locking stent with locking mechanisms less prone to damage.
Another consideration in the design of the stent 100 relates to its cross-sectional shape. As shown in a cross-section view in FIG. 1B, the stent 100 has a semi-rounded cross-section due to an apex 106 formed adjacent the seam 102 and/or locking mechanisms 104. Vessels are generally round so it is advantageous to provide a stent that has a complementary cross-sectional shape. This would optimize the delivery of a therapeutic agent to the vessel (i.e., by maximizing surface contact). In some instances, however, vessels are not absolutely round, but are more-or-less “irregularly” shaped. The presence of plaque and/or lesions may contribute to changes in shape. Numerous stent cross-sectional shapes, including rounded and semi-rounded types, may not conform to an “irregularly” shaped vessel. As such, it would be desirable to provide a stent with a cross-sectional shape that is capable of conforming to the vessel.
Another consideration in the design of the stent 100 relates to profile size (i.e., cross-sectional diameter). It is often desirable to provide a small profile size as advancement of a device within the vasculature oftentimes includes navigating many sharp twists, turns, and narrow spaces. Relatively large devices may be more difficult to maneuver through a sometimes tortuous vasculature. Devices with smaller profiles may be less prone to contact the vascular walls during advancement and impart damage to the delicate endothelium. As such, it would be desirable to provide a stent with a relatively small profile size. Furthermore, devices with smaller profiles could better transverse tight lesions where plaque has closed off much of the vessel lumen.
Accordingly, it would be desirable to provide an intraluminal stent, delivery system, and method of treating a vascular condition that would overcome the aforementioned and other limitations.